Semiconductor device and method of manufacturing the same

ABSTRACT

A first semiconductor chip is produced by affixing a thermo-compression sheet to the back surface of a wafer having a circuit formed on its front surface. The first semiconductor chip is mounted on a circuit board including an insulating substrate and a wiring layer provided on the insulating substrate so that the back surface of the first semiconductor chip faces the circuit board. A second semiconductor chip produced in the same manner as the first semiconductor chip is mounted on the first semiconductor chip with its back surface facing the first semiconductor chip. Each of the first and second semiconductor chips is wire-bonded to the wiring layer with a wire. The first and second semiconductor chips and the wire are sealed with a sealing resin. The wiring layer is connected to external connection terminals through via holes provided in the insulating substrate.

This is a continuation of application Ser. No. 09/223,272, filed Dec.30, 1998, now U.S. Pat. No. 6,100,594, the entire content of which ishereby incorporated by reference in this application.

FIELD OF THE INVENTION

The present invention relates to a semiconductor device and a method ofmanufacturing the same, and more particularly relates to a semiconductordevice having a structure substantially miniaturized to a chip size,i.e., a CSP (Chip Size Package) structure, and a method of manufacturingsuch a semiconductor device.

BACKGROUND OF THE INVENTION

Miniaturization of a semiconductor device is in progress so as toachieve a high-density semiconductor device for use on a printed circuitboard. Recently, a semiconductor device substantially miniaturized to achip size has been developed. The structure of such a miniaturizedsemiconductor device is called a CSP structure. Japanese Publication ofUnexamined Patent Application No. 121002/1997 (Tokukaihei 9-121002)discloses a semiconductor device having the CSP structure shown in FIG.13(a). This semiconductor device includes a semiconductor chip 42disposed with its circuit formed surface facing up, and wires 43 forelectrically connecting the semiconductor chip 42 to a wiring pattern47. The above publication discloses another semiconductor device havingthe CSP structure shown in FIG. 13(b). This semiconductor deviceincludes a semiconductor chip 64 disposed with its circuit formedsurface facing down, and a bump electrode 70 for electrically connectingthe semiconductor chip 64 to a wiring pattern 66.

In FIG. 13(a), 41 is a wiring component, 42 is a semiconductor chip, 43is a wire, 44 is a resin sealing member, 45 is a throughhole, 46 is asubstrate, 47 is a wiring pattern, 48 is an insulating material, 49 isan external connection-use terminal, 50 is an external connection area,51 is an electrode, 52 is a window opening section, and 53 is an innerconnection area. In FIG. 13(b), 61 is a throughhole, 62 is a wiringcomponent, 63 is an electrode, 64 is a semiconductor chip, 65 is a resinsealing member, 66 is a wiring pattern, 67 is an inner connection area,68 is an external connection area, 69 is an external connection-useterminal, and 70 is a bump electrode.

In some devices such as portable devices, a plurality of semiconductorchips are mounted in a package so as to increase the added value andcapacity of memory, etc. For example, a multi-chip module is providedwith a plurality of semiconductor chips arranged parallel to each otherin a package. However, such an arrangement makes it impossible toproduce a package smaller than the total area of the semiconductor chipsto be mounted. In order to solve the problem, a stacked packageincluding a plurality of semiconductor chips laminated in a package toachieve a high packaging density is disclosed in Japanese Publication ofUnexamined Patent Application No. 90486/1993 (Tokukaibei 5-90486).

Specifically, the semiconductor devices disclosed in the abovepublication are each packaged in ceramic packages and arranged in thefollowing manner. In one of the semiconductor devices, a pair ofsemiconductor chips are adhered to each other with their back surfaceswhere a circuit is not formed facing each other, and are mounted onanother pair of semiconductor chips via metal bumps. In the othersemiconductor device, a pair of semiconductor chips are adhered to eachother with the circuit formed surface of one semiconductor chip facingthe back surface of the other semiconductor chip.

The above-mentioned stacked package is a small high-densitysemiconductor device. However, a semiconductor device smaller than sucha stacked package has been required. For that reason, a semiconductordevice having a CSP structure as well as a stacked package structure isrequired to be produced.

In a semiconductor device having a CSP structure where the semiconductorchips are laminated, an adhesive agent (paste) potting method and amethod using a thermo-compression sheet are utilized for bonding thesemiconductor chip to the substrate, and for bonding the laminatedsemiconductor chips to each other.

In the potting method, if the amount of the adhesive agent is excessive,a large amount of adhesive agent spreads beyond the outer edge of thesemiconductor chip. For example, as shown in FIG. 14(a), when bondingsemiconductor chips 81 and 82 to each other with their back surfacesfacing each other, an adhesive agent 87 between the semiconductor chips81 and 82 overflows. In addition, as shown in FIG. 15, in the step ofwire-bonding the semiconductor chip 82 disposed on the top to anelectrode section of a wiring layer 84 (before a sealing resin 89 andpackaging-use external terminals 90 are formed), wiring on an insulatingsubstrate 83 must be provided far from the side surfaces of thesemiconductor chips 81 and 82 so as to keep the overflown adhesive agent87a from coming into contact with a jig 92 of a wire bonder. Such anarrangement causes the package size to be increased in the end.Furthermore, as shown in FIG. 14(b), when bonding the back surface ofthe semiconductor chip 82 to the circuit formed surface of thesemiconductor chip 81, the overflown adhesive agent 87a may stick to anelectrode pad provided on the semiconductor chip 81.

On the other hand, if the amount of the adhesive agent is too small, agap is produced between the semiconductor chips 81 and 82. This gapcannot be filled with the sealing resin 89, thereby causing problemssuch as separation of the semiconductor chip 82 from the semiconductorchip 81.

The method using a thermo-compression sheet requires the steps ofplacing members at the right locations. Specifically, athermo-compression sheet having the same size as the semiconductor chip82 must be placed accurately at a specific location on the semiconductorchip 81. In addition, the semiconductor chip 82 must be bonded to thethermo-compression sheet so as to be located exactly on the top of thethermo-compression sheet.

In FIGS. 14(a) and 14(b), 85 is an insulating sheet, 86 is a metal bump,and 91 is an adhesive sheet.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a further-miniaturizedsemiconductor device having a stacked package structure as well as a CSPstructure.

In order to achieve the above object, a semiconductor device inaccordance with the present invention has a stacked package structureand a chip size package structure and is characterized in including:

-   -   an insulating substrate including a wiring layer having        electrode sections;    -   a first semiconductor chip having a first insulating adhesion        layer adhered to its back surface where a circuit is not formed,        the first semiconductor chip being mounted on the wiring layer        through the first insulating adhesion layer; and    -   a second semiconductor chip having a second insulating adhesion        layer adhered to its back surface where a circuit is not formed,        the second semiconductor chip being mounted on a circuit-formed        front surface of the first semiconductor chip through the second        insulating adhesion layer;    -   each of the first and second semiconductor chips being        wire-bonded to the electrode section with a wire, the first and        second semiconductor chips and the wire being sealed with a        resin.

In the above structure, the first semiconductor chip and the secondsemiconductor chip are each wire-bonded to the electrode sectionprovided on the wiring layer with the wires, and the second insulatingadhesion layer is used for affixing the second semiconductor chip to thefirst semiconductor chip. This structure eliminates the need forwire-bonding the first and second semiconductor chips to points on thewiring layer, far from the side surfaces of the first and secondsemiconductor chips, considering a situation in which the excessivelyapplied adhesive agent overflows the space between the first and secondsemiconductor chips. Therefore, a miniaturized, high-densitysemiconductor device can be realized.

Furthermore, in the case of using a thermo-compression sheet, whenmounting the first or second semiconductor chip at a desired location,accurate positioning is required twice, i.e., positioning thethermo-compression sheet, etc., and positioning the first or secondsemiconductor chip on the thermo-compression sheet. In contrast, thefirst and second insulating adhesion layers according to the presentinvention are in advance disposed on the back surfaces of the first andsecond semiconductor chips, respectively. Therefore, the first or secondsemiconductor chip can be mounted at a desired location by accuratelypositioning it once. It is thus possible to miniaturize thesemiconductor device without complicating its manufacturing process.

A semiconductor device in accordance with the present invention can bearranged to include:

-   -   an insulating substrate including a wiring layer having        electrode sections;    -   a first semiconductor chip having a circuit formed on its front        surface and an insulating adhesion layer adhered to its back        surface;    -   a metal bump, disposed between the first semiconductor chip and        the wiring layer, for bump-bonding the front surface of the        first semiconductor chip to the wiring layer so that the front        surface faces the wiring layer; and    -   a second semiconductor chip whose back surface where a circuit        is not formed is mounted on the back surface of the first        semiconductor chip through the insulating adhesion layer;    -   the second semiconductor chip being wire-bonded to the electrode        section of the wiring layer with a wire, the first and second        semiconductor chips and the wire being sealed with a resin.

In the above arrangement, the first semiconductor chip is connected tothe wiring layer through the metal bump, the second semiconductor chipis wire-bonded to the electrode sections on the wiring layer with wires,and the back surfaces of the first and second semiconductor chips areadhered to each other by the insulating layer. This arrangementeliminates the need for wire-bonding the second semiconductor chip topoints on the wiring layer, far from the side surfaces of the first andsecond semiconductor chips, considering a situation in which theexcessively applied adhesive agent overflows the space between the firstand second semiconductor chips. Therefore, a miniaturized, high-densitysemiconductor device can be realized.

In the case of using the thermo-compression sheet, when mounting thesecond semiconductor chip on the first semiconductor chip, accuratepositioning is required twice in a conventional manufacturing method,i.e., positioning the thermo-compression sheet on the firstsemiconductor chip, and positioning the second semiconductor chip on thethermo-compression sheet. However, the insulating adhesion layeraccording to the present invention are disposed on the back surface ofthe second semiconductor chip in advance. Therefore, the secondsemiconductor chip can be mounted at a desired location on the firstsemiconductor chip by accurately positioning it once. It is thuspossible to miniaturize the semiconductor chip without complicating itsmanufacturing process.

A method of manufacturing a semiconductor device in accordance with thepresent invention includes the steps of:

-   -   (a) forming a first insulating adhesion layer on a back surface        of a first wafer having a circuit formed on its front surface;    -   (b) producing separate first semiconductor chips from the first        wafer by dicing;    -   (c) mounting the first semiconductor chip on a wiring layer with        its back surface facing the wiring layer;    -   (d) forming a second insulating adhesion layer on a back surface        of a second wafer having a circuit formed on its front surface;    -   (e) producing separate second semiconductor chips from the        second wafer by dicing;    -   (f) mounting the second semiconductor chip on the first        semiconductor chip with its back surface facing the first        semiconductor chip;    -   (g) wire-bonding the first semiconductor chip to an electrode        section of the wiring layer with a wire;    -   (h) wire-bonding the second semiconductor chip to an electrode        section of the wiring layer with a wire; and    -   (i) sealing the first and semiconductor chips and the wires.

With the above manufacturing method, since the first or secondsemiconductor chip has the first or second insulating adhesion layeradhered to its back surface in advance when being in the wafer state,the first or second semiconductor chip can be mounted at a desiredlocation without the step of accurately positioning the first or secondinsulating adhesion layer on the first or second semiconductor chip. Itis thus possible to simplify the process of manufacturing thesemiconductor chip.

Moreover, in the above manufacturing method, the adhesive agent does notoverflow the space between the first and second semiconductor chips, thefirst and second semiconductor chips can be wire-bonded to the wiringlayer at a location closer to the edges of the first and secondsemiconductor chips. It is thus possible to realize a miniaturized,high-density semiconductor device.

A method of manufacturing a semiconductor device in accordance with thepresent invention including the steps of:

-   -   (a) forming an insulating layer and a metal bump on a wiring        layer;    -   (b) mounting a first semiconductor chip on the wiring layer with        its circuit-formed surface facing the wiring layer;    -   (c) forming an insulating adhesion layer on a back surface of a        wafer having a circuit formed on its front surface;    -   (d) producing separate second semiconductor chips from the wafer        by dicing;    -   (e) mounting the second semiconductor chip on the first        semiconductor chip with its back surface facing the first        semiconductor chip;    -   (f) wire-bonding the second semiconductor chip to the wiring        layer with a wire; and    -   (g) sealing the first and second semiconductor chips and the        wire.

In this manufacturing method, like the above-mentioned method of thepresent invention, since the second semiconductor chip has theinsulating adhesion layer adhered to its back surface in advance whenbeing in the wafer state, the second semiconductor chip can be mountedat a desired location without the step of accurately positioning theinsulating adhesion layer on the second semiconductor chip. It is thuspossible to simplify the process of manufacturing the semiconductorchip.

Furthermore, in the above manufacturing method, the adhesive agent doesnot overflow the space between the first and second semiconductor chips,the second semiconductor chip can be wire-bonded to the wiring layer ata location closer to the edges of the first and second semiconductorchips. It is thus possible to realize a miniaturized, high-densitysemiconductor device.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a semiconductor device in accordancewith the first embodiment of the present invention.

FIG. 2(a) is a plan view of a circuit board before being cut, and FIG.2(b) is a partially enlarged view of the circuit board shown in FIG.2(a).

FIG. 3(a) is an explanatory view showing an arrangement of ball-likeexternal connection-use terminals, and FIG. 3(b) is an explanatory viewshowing an arrangement of trapezoidal external connection-use terminals.

FIG. 4 is an explanatory view showing how laminated semiconductor chipsare each wire-bonded to the circuit board.

FIGS. 5(a) to 5(g) show one example of a process of manufacturing thesemiconductor device.

FIG. 6(a) is a partially enlarged view of the circuit board including awiring layer disposed on one surface of an insulating substrate, andFIG. 6(b) is a partially enlarged view of a circuit board including awiring layer disposed on each surface of the insulating substrate.

FIG. 7(a) is an explanatory view showing a wiring state when twolaminated semiconductor chips are connected to the same electrodesection, and FIG. 7(b) is an explanatory view showing another state thatthe two laminated semiconductor chips are connected to the sameelectrode section.

FIG. 8(a) is an explanatory view showing a wiring state that the twolaminated semiconductor chips are connected to different electrodesections, and FIG. 8(b) is an explanatory view showing another wiringstate that the two laminated semiconductor chips are connected todifferent electrode sections.

FIG. 9(a) is an explanatory view showing one example of an arrangementof dummy pads formed on a first semiconductor chip, and FIG. 9(b) is anexplanatory view showing another example of the arrangement of the dummypads disposed on the first semiconductor chip.

FIG. 10 is a cross-sectional view of a semiconductor device inaccordance with the second embodiment of the present invention.

FIGS. 11(a) to 11(g) show one example of a process for manufacturing thesemiconductor device.

FIG. 12(a) is a perspective view showing that a second semiconductorchip in the semiconductor device in accordance with the first embodimentor the second embodiment protrudes from a first semiconductor chip, andFIG. 12(b) is a perspective view showing that the second semiconductorchip is reinforced.

FIG. 13(a) is a cross-sectional view showing a semiconductor devicehaving a CSP structure manufactured by a conventional wire bondingmethod, and FIG. 13(b) is a cross-sectional view showing a semiconductordevice having a CSP structure manufactured by a conventional face-downbonding method.

FIGS. 14(a) and 14(b) are cross-sectional views of conventionalsemiconductor devices having a stacked package structure.

FIG. 15 is a cross-sectional view of the semiconductor device shown inFIG. 14(a) during manufacturing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

The following descriptions will explain one embodiment of the presentinvention with reference to FIGS. 1 to 9.

As shown in FIG. 1, in a semiconductor device according to thisembodiment, a first semiconductor chip 1 and a second semiconductor chip2 are laminated in this order on a circuit board 5 including aninsulating substrate 3 and a wiring layer 4 mounted on the insulatingsubstrate 3. Regarding the first semiconductor chip 1 and the secondsemiconductor chip 2, the surface (front surface) on which an element isformed is hereinafter referred to as a “circuit formed surface”, and thesurface opposite thereto is referred to as a “back surface”.

The semiconductor chip 1 is disposed with its back surface facing theinsulating substrate 3. The second semiconductor chip 2 is mounted onthe circuit formed surface of the first semiconductor chip 1 through athermo-compression sheet (adhesion layer) 6 so that its back surface isadhered to the thermo-compression sheet 6.

The semiconductor device in accordance with the present embodiment isarranged so that the second semiconductor chip 2 is mounted on thecircuit formed surface of the first semiconductor chip 1. With thisarrangement, the second semiconductor chip 2 on the top of the firstsemiconductor chip 1 does not influence (interfere with) electrode padsof the first semiconductor chip 1. The circuit formed surface of thefirst semiconductor chip 1 is in advance coated with aninsulating-resin, etc. Namely, the coating is applied to the circuitformed surface of the first semiconductor chip 1 by a spin coatingmethod, etc. when the first semiconductor chip 1 is in a wafer statebefore subjected to dicing. In this case, the coating material on theelectrode pads (not shown) disposed on the circuit formed surface of thefirst semiconductor chip 1 is removed.

The first semiconductor chip 1 and the second semiconductor chip 2 areeach connected (wire-bonded) to electrode sections of the wiring layer 4on the insulating substrate 3 with wires 7.

The first semiconductor chip 1, the second semiconductor chip 2 and thewires 7, arranged as above, are covered by a sealing resin 8.

The insulating substrate 3 includes via holes 9 at the locationscorresponding to below-described land sections 12 constituting thewiring layer 4. Ball-like packaging-use external terminals 10 areconnected in an area-array-like arrangement to the land sections 12through the via holes 9 from the side of the insulating substrate 3, onwhich side the first semiconductor chip 1 and the second semiconductorchip 2 are not formed.

Next, the following descriptions will explain in further detail theabove-mentioned members constituting the semiconductor device inaccordance with the present embodiment.

FIG. 2(a) is a plan view of the circuit board 5 before being cut in theprocess of manufacturing the semiconductor device. As shown in FIG.2(a), four guide holes 11 are formed in both side sections of theinsulating substrate 3 (the upper part and the lower part of theinsulating substrate 3 in FIG. 2(a)) of the circuit board 5 before beingcut. The guide holes 11a formed in one of the side section and the guideholes 11b formed in the other side section have different shapes. Theseguide holes 11 are used for transporting the semiconductor device duringits manufacturing process.

The material of the insulating substrate 3 is not particularly limited,and a resin substrate or a film having excellent heat resistance isacceptable. The insulating material 3 may be a resin substrate, etc.made of, for example, polyimide, epoxy resin containing glass fiber,bismaleid triazine (BT) resin, polyester, polyamide, fluororesin,ceramic, and polyester containing glass fiber. Polyimide is the mostpreferable of the above materials.

FIG. 2(b) is a partially enlarged view of the circuit board 5 shown inFIG. 2(a), showing the structure of the wiring layer 4. As shown in FIG.2(b), the wiring layer 4 includes the land sections 12, electrodesections 13, and wiring sections 14, disposed on the insulatingsubstrate 3. Each of the wiring sections 14 connects the land section 12to the electrode section 13.

The electrode sections 13 are formed on both ends of the wiring layer 4(the left part and the right part of the wiring layer 4 in FIG. 2(b)).As explained in detail later, each of the electrode section 13 isconnected to the first semiconductor chip 1 or the second semiconductorchip 2 by the wire 7. Therefore, the electrode sections 13 are locatedoutside the area of the wiring layer 4, where the first semiconductorchip 1 and the second semiconductor chip 2 are mounted.

The land section 12 is a packaging-use external terminal forming sectionfor connecting the packaging-use external terminal 10 and the wiringlayer 4 through the via hole 9 of the insulating substrate 3.

The first semiconductor chip 1 can be completely insulated from thewiring layer 4 by, for example, providing a sheet of an insulating resinon an area of the wiring layer 4 where the first semiconductor chip 1 isto be mounted or applying an insulating resin coating to the area of thewiring layer 4. The wiring layer 4 is made of copper (Cu), aluminum(Al), gold (Au), nickel (Ni), and other materials. Cu is particularlypreferable because it is less costly. Methods of forming the wiringlayer 4 on the insulating substrate 3 include a vapor deposition methodand a plating method. In order to pattern the wiring layer 4 to form adesired pattern, a conventional photolithography method can be utilized.

FIG. 3(a) is a view seen from the back side of the semiconductor deviceshown in FIG. 1, i.e., the side where the packaging-use externalterminals 10 are disposed. As shown in FIG. 3(a), ball-likepackaging-use external terminals 10 are disposed in an area-array-likearrangement, and connected to the land sections 12 provided on thewiring layer 4. The packaging-use external terminals 10 are not limitedto a ball-like shape, and may have a trapezoidal shape as shown in FIG.3(b).

Each of the wires 7 is used for connecting the electrode pad disposed onthe first semiconductor chip 1 or the second semiconductor chip 2 to theelectrode section 13 of the wiring layer 4. In a conventionalsemiconductor device, a gold ball provided on only one end of the wireis in contact with the electrode pad of the first semiconductor chip orthe second semiconductor chip, and the other end of the wire isconnected to the electrode section of the wiring layer on the insulatingsubstrate. Here, the gold ball can be provided on only one end of thewire. The gold ball is brought into contact with the electrode pad byimposing a load lighter than the load applied in connecting, bythermo-compression bonding, the wire to the electrode section of thewiring layer on the insulating substrate. This is because connecting thewires to the semiconductor chips by thermo-compression bonding, i.e., byapplication of a heavy load, increases the possibility of damaging thesemiconductor chips.

However, the above conventional arrangement has the following problem.Namely, the wires, especially those connected to the secondsemiconductor chip, are connected to the electrode sections of thewiring layer provided on the circuit board at a small angle with respectto the circuit board. Therefore, the wire is connected to the circuitboard, far from the end of the first semiconductor chip.

In order to solve the problem, in the semiconductor device according tothe present embodiment, the first semiconductor chip 1 and the secondsemiconductor chip 2 are each wire-bonded to the circuit board 5 asshown in FIG. 4. The first semiconductor chip 1 and the circuit board 5are wire-bonded in the same manner as the conventional semiconductordevice. Then, the wire 7 is connected to the circuit board 5 with a goldball 7a provided on one end of the wire 7. Thereafter, the other end ofthe wire 7 is connected, by thermo-compression boding, to a gold bump 16formed on the electrode pad of the second semiconductor chip 2 inadvance so as to connect the second semiconductor chip 2 to the circuitboard 5.

Since wire-bonding between the second semiconductor chip 2 and thecircuit board 5 is performed as above, the wire 7 connected to thesecond semiconductor chip 2 is connected to the circuit board 5 at anangle closer to 90° with respect to the circuit board 5. Therefore, thewire 7 is connected to the circuit board 5 at a closer location to theend of the first semiconductor chip 1, thereby enabling furtherminiaturization of the semiconductor device in accordance with thepresent embodiment.

The wire 7 is connected to the gold bump 16 by thermo-compressionbonding by a load nearly equal to the load applied when connecting thewire 7 to the electrode section of the wiring layer 4 on the insulatingsubstrate 3 by thermo-compression bonding. However, by using the goldbump 16, the stress applied to the second semiconductor chip 2 can belowered. It is thus possible to reduce the possibility that the secondsemiconductor chip 2 is damaged by a heavy load applied thereto.

The gold bump 16 is formed by connecting a gold ball, provided on theend of the wire by the conventional method, to the electrode pad on thesecond semiconductor chip 2, and then cutting the wire 7. Thereafter, bymaking the upper surface of the gold bump 16 flat with a stamping jig,the wire 7 can be surely affixed to the gold bump 16 bythermo-compression bonding.

Note that the first semiconductor chip 1 and the circuit board 5 can bewire-bonded to each other in the same manner as the above-mentionedwire-bonding of the second semiconductor chip 2 and the circuit board 5.

The following descriptions will explain one example of the process(including steps (1) to (5)) for manufacturing the semiconductor devicein accordance with the present embodiment with reference to FIGS. 5(a)to 5(g).

(1) First, the first semiconductor chip 1 is mounted on the circuitboard 5 (see FIG. 5(a)). When the first semiconductor chip 1 is in awafer state, the insulating thermo-compression sheet 6 is adhered to theback surface of the wafer. Then, the wafer is cut to produce separatepieces of first semiconductor chips 1. The first semiconductor chip 1 ismounted on the circuit board 5 at a location inside a mount locationrecognition-use mark 15 provided on the circuit board 5. Here, insteadof providing the thermo-compression sheet 6 in advance when the firstsemiconductor chip 1 is in the wafer state, an insulating paste made ofepoxy resins, etc. may be applied onto the circuit board 5 before thefirst semiconductor chip 1 is mounted on the circuit board 5.

(2) Next, the second semiconductor chip 2 is mounted on the circuitformed surface of the first semiconductor chip 1 (see FIG. 5(b)). Whenthe second semiconductor chip 2 is in the wafer state, the insulatingthermo-compression sheet 6 is adhered to the back surface of the wafer,and then the wafer is cut to produce separate pieces of secondsemiconductor chips 2. The second semiconductor chip 2 is accuratelypositioned at a specific location on the circuit formed surface of thefirst semiconductor chip 1.

By affixing the thermo-compression sheet 6 to the back surface of thesecond semiconductor chip 2 in advance, accurate positioning isnecessary only when mounting the second semiconductor chip 2 on thefirst semiconductor chip 1. Therefore, since one step requiring accuratepositioning is omitted in the process for manufacturing thesemiconductor device in accordance with the present embodiment, thismanufacturing process is simplified compared with the conventionalprocess in which the thermo-compression sheet 6 is disposed on thecircuit formed surface of the first semiconductor chip 1, and then thesecond semiconductor chip 2 is adhered to the thermo-compression sheet6.

(3) Then, each of the electrode pads (not shown) disposed on the firstsemiconductor chip 1 and the second semiconductor chip 2 is connected,with the wire 7 made of Au, to the electrode section 13 formed in thewiring layer 4 on the circuit board 5. More specifically, the firstsemiconductor chip 1 and the wiring layer 4 are first electricallyconnected to each other (see FIG. 5(c)), and then the secondsemiconductor chip 2 and the wiring layer 4 are electrically connectedto each other (see FIG. 5(d)). Since the first semiconductor chip 1 andthe second semiconductor chip 2 are each electrically connected to thewiring layer 4 in the above order, it is possible to avoid such aproblem that the wire 7 for connecting the first semiconductor chip 1 tothe circuit board 5 and the wire 7 for connecting the secondsemiconductor chip 2 to the circuit board 5 across each other, andprevent connection of the first semiconductor chip 1 to the circuitboard 5.

(4) Thereafter, each of the packaging-use external terminals 10 isdisposed on the location where the via hole 9 is provided on theinsulating substrate 3 on the circuit board 5 (see FIG. 5(f)). Here,positioning the packaging-use external terminal 10 is performed in sucha manner that a solder ball is temporarily fixed to each via hole 9,heated in a reflow furnace, and then joined to the land section 12.Methods of temporarily fixing the solder ball to the via hole 9 includea method in which the solder ball is affixed to the via hole 9 afterapplying a flux to the via hole 9, and a method in which the solder ballis affixed to the via hole 9 after adhering the flux to the solder ball.

(5) Finally, a plurality of semiconductor devices produced on thecircuit board 5 are divided into pieces of semiconductor devices (seeFIG. 5(d)) by cutting the insulating substrate 3 along its unnecessarypart, i.e., along the outer edge of the sealing resin 8 of eachsemiconductor device. Methods of cutting the insulating substrate 3include a punching method using die, and an eximer laser cutting method.

As shown in FIG. 6(a), the semiconductor device in accordance with thepresent embodiment includes the wiring layer 4 on only one of thesurfaces of the insulating substrate 3. However, the wiring layer 4 canbe provided on both surfaces of the insulating substrate 3 as shown inFIG. 6(b).

When the wiring layer 4 is formed on both surfaces of the insulatingsubstrate 3, as shown in FIG. 6(b), the wiring layers 4 on therespective surfaces are electrically connected to each other through theplated via holes 9 as shown in FIG. 6(b). Regarding the wiring layer 4on the side of the insulating substrate 3, the side where the firstsemiconductor chip 1 is not mounted, the area where the packaging-useexternal terminals 10 are not to be formed are covered with a solderresist 20, etc. In the area which is not covered with the solder resist20, i.e., the area where the packaging-use external terminals 10 are tobe provided, the packaging-use external terminals 10 are arranged in anarea-array-like pattern.

When connecting the first semiconductor chip 1 and the secondsemiconductor chip 2 to the electrode sections 13 of the wiring layer 4with the wires 7, if the wires 7 become too close to each other becauseof the layout of the electrode pads of the first semiconductor chip 1and the second semiconductor chip 2, the wires 7 can be arranged asbelow.

When connecting the first semiconductor chip 1 and the secondsemiconductor chip 2 to the same electrode section 13 of the wiringlayer 4, two arrangements shown in FIGS. 7(a) and 7(b) are acceptable.In the arrangement shown in FIG. 7(a), the electrode section 13 of thewiring layer 4, to which two wires 7 are connected, is arranged to havetwo parts. In the arrangement shown in FIG. 7(b), an electrode pad 17aof the first semiconductor chip 1 is connected to an electrode pad 17bof the second semiconductor chip 2 with the wire 7, and the electrodepad 17a is connected to the electrode section 13 of the wiring layer 4with the wire 7, thereby connecting each of the electrode pads 17a and17b to the electrode section 13.

When connecting the first semiconductor chip 1 and the secondsemiconductor chip 2 to different electrode sections 13 of the wiringlayer 4, two arrangements shown in FIGS. 8(a) and 8(b) are acceptable.In the arrangement shown in FIG. 8(a), the electrode pad 17a of thefirst semiconductor chip 1 and the electrode pad 17b of the secondsemiconductor chip 2 are each connected directly to the electrodesection 13 of the wiring layer 4 with the wire 7. In the arrangementshown in FIG. 8(b), dummy pads 18 are provided on the firstsemiconductor chip 1, and the electrode pad 17b disposed on the secondsemiconductor chip 2 is connected to the electrode section 13 of thewiring layer 4 via the dummy pad 18. This arrangement shown in FIG. 8(b)is more preferable because the overhanging part of the wire 7 is shorterthan that in the arrangement shown in FIG. 8(a).

FIGS. 9(a) and 9(b) show examples of the arrangement of the dummy pads18 provided on the first semiconductor chip 1.

Embodiment 2

With reference to FIGS. 10 to 12, the following descriptions willexplain the second embodiment of the present invention. The membershaving the same structure as those in the above-mentioned firstembodiment will be designated by the same reference numbers and theirdescription will be omitted.

A semiconductor device in accordance with the present embodiment isarranged as shown in FIG. 10. Specifically, a first semiconductor chip21 is mounted on a circuit board 5 with its circuit formed surfacefacing the circuit board 5, i.e., facing down. The circuit board 5includes an insulating substrate 3, and a wiring layer 4 formed on theinsulating substrate 3. A second semiconductor chip 22 is mounted on theback surface of the first semiconductor chip 21 through athermo-compression sheet 6. The back surface of the second semiconductorchip 22 faces the first semiconductor chip 21. Namely, the back surfacesof the first semiconductor chip 21 and the second semiconductor chip 22are adhered to each other through the thermo-compression sheet 6. Thethermo-compression sheet 6 is provided as an adhesion layer for holdingthe second semiconductor chip 22 on the first semiconductor chip 21.

The first semiconductor chip 21 is electrically connected to firstelectrode sections (not shown) provided in the wiring layer 4 throughmetal bumps 23. The first electrode sections are disposed inside an areaof the wiring layer 4, where the first semiconductor chip 21 is mounted.

Meanwhile, the second semiconductor chip 22 is electrically connected tosecond electrode sections (not shown) provided in the wiring layer 4with wires 7. Since the second electrode sections are used forwire-bonding the second semiconductor chip 22 to the wiring layer 4,they are disposed outside the area of the wiring layer 4, where thefirst semiconductor chip 21 and the second semiconductor chip 22 aremounted.

A resin sheet 24 is provided between the first semiconductor chip 21 andthe wiring layer 4. The resin sheet 24 is formed by extending a resinsheet used in the step of connecting the first semiconductor chip 21 tothe wiring layer 4 through the metal bumps 23.

If electrode pads provided on the circuit formed surface of the firstsemiconductor chip 21 are made of Al, the metal bumps 23 are preferablymade of Au which is easily alloyed with Al. With this arrangement, themetal bumps 23 can be more firmly affixed to the electrode pads.

The material for forming the resin sheet 24 may be a thermoplastic resinor a thermosetting resin. However, the thermoplastic resin is morefavorable than the thermosetting resin because the resin sheet 24 isused for the following purpose. Namely, it is used so that the resinextends by heat applied in connecting the first semiconductor chip 21 tothe wiring layer 4 with the metal bumps 23, covers the metal bumps 23 asjunctions, and prevents degradation of the junctions caused by shock,etc.

The resin sheet 24 can be a three-layer resin sheet including a layer ofa light blocking material such as metallic foil. With this arrangement,it is possible to prevent a malfunction of the first semiconductor chip21 due to a light incident from the surface where the packaging-useexternal terminals 10 are mounted passing through the semiconductordevice. In this case, the size of the metallic foil must be such thatthe metallic foil is out of contact with the metal bumps 23.

Although the semiconductor device in accordance with the presentembodiment uses the resin sheet 24, the following arrangement is alsoacceptable. Namely, the semiconductor chip 21 is mounted without usingthe resin sheet 24, and then the space produced at a junction of thefirst semiconductor chip 21 and the wiring layer 4 is filled with aliquid resin, etc., thereby covering the metal bumps 23 as thejunctions.

Next, referring to FIGS. 11(a) to 11(g), the following descriptions willexplain the process (including steps (1) to (7)) for manufacturing thesemiconductor device in accordance with the present embodiment.

(1) First, the resin sheet 24 and the metal bumps 23 are disposed on thecircuit board 5 (see FIG. 11(a)). In this case, each of the metal bumps23 is disposed on the first electrode section provided in the wiringlayer 4 on the circuit board 5. The resin sheet 24 is disposed on thecircuit board 5 at the location where the first semiconductor chip 21and the second semiconductor chip 22 are to be mounted.

(2) Next, the first semiconductor chip 21 is connected to the wiringlayer 4 on the circuit board 5 by a flip chip method in a face-down mode(see FIG. 11(b)).

(3) Then, the second semiconductor chip 22 is mounted on the backsurface of the first semiconductor chip 21 (see FIG. 11(c)). When thesecond semiconductor chip 22 is in a state of wafer, the insulatingthermo-compression sheet 6 is adhered to the back surface of the wafer,and then the wafer is cut to produce chips, i.e., separate pieces ofsecond semiconductor chips 22. The second semiconductor chip 22 isaccurately positioned at a specific location on the circuit formedsurface of the first semiconductor chip 21.

Like the manufacturing process described in the first embodiment, theprocess for manufacturing the semiconductor device in accordance withthe present embodiment is simplified by adhering the thermo-compressionsheet 6 to the back surface of the second semiconductor chip 22 inadvance.

(4) Then, the second semiconductor chip 22 is electrically connected tothe wiring layer 4 on the circuit board 5 (see FIG. 11(d)). morespecifically, each of the electrode pads disposed on the circuit formedsurface of the second semiconductor chip 22 is connected to the secondelectrode section of the wiring layer 4 with the wire 7.

(5) Thereafter, the first semiconductor chip 21, the secondsemiconductor chip 22, and the wires 7, provided on the circuit board 5,are sealed with a sealing resin 8 (see FIG. 11(e)). The method offorming the sealing resin 8 is similar to that described in the firstembodiment.

(6) Then, each of the packaging-use external terminals 10 is disposed ata location of a via hole 9 formed in the insulating substrate 3 of thecircuit board 5 (see FIG. 11(f)).

(7) Finally, a plurality of semiconductor devices produced on thecircuit board 5 are divided into pieces of semiconductor devices bycutting the insulating substrate 3 along the unnecessary part of theinsulating substrate 3 of the circuit board 5, i.e., along the outeredge of the sealing resin 8 of each semiconductor device unnecessaryparts (see FIG. 11(d)). The methods of cutting the insulating substrate3 including a punching method using a die, and an eximer laser method.

In the above-described first embodiment (and in the second embodiment),when mounting the second semiconductor chips 2 (22) on the firstsemiconductor chips 1 (21), if the first semiconductor chips 1 (21) andthe second semiconductor chips 2 (22) have different shapes, the secondsemiconductor chips 2 (22) may protrude from the first semiconductorchips 1 (21) as shown in FIG. 12(a). In this case, since the protrudedpart of the second semiconductor chip 2 (22) is of low strength, thesecond semiconductor chip 2 (22) may be possibly destroyed by shockproduced when, for example, wire-bonding the electrode pads 17b of thesecond semiconductor chip 2 (22) to the wiring layer 4.

In order to solve the problem, as shown in FIG. 12(b), a support member19 having the same height and the same shape as the first semiconductordevice 1 (21) is fixed under the protruded part of the secondsemiconductor chip 2 (22). By reinforcing the second semiconductor chip2 (22) with the support member 19, destruction thereof can be prevented.The support member 19 is preferably made of Silicon (Si) in order toreduce generation of stress, etc. against a heat load applied during andafter manufacturing the semiconductor device with the CSP structure. Inaddition, the support member 19 has the same coefficient of linearexpansion as the second semiconductor chip 2 (22).

The above-mentioned semiconductor devices in accordance with Embodiments1 and 2 include two laminated semiconductor chips. However, the presentinvention can be arranged to include three or more laminatedsemiconductor chips. In this case, the third semiconductor chip can bemounted on the top of the two semiconductor chips with its circuitformed surface facing up and wire-bonded to the wiring layer 4.Alternatively, the third semiconductor chip can be mounted on the top ofthe two semiconductor chips with its circuit formed surface facing downthrough metal bumps by providing electrode pads for disposing the metalbumps on the circuit formed surface of the second semiconductor chip 2(22).

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. A semiconductor device including a stacked package structure and achip size package structure, comprising: an insulating substrateincluding a wiring layer having electrode sections; a firstsemiconductor chip having a first adhesion layer adhered to its backsurface where a circuit is not formed, said first semiconductor chipbeing mounted on said wiring layer through the first insulating adhesionlayer; and a second semiconductor chip having a second adhesion layeradhered to its back surface where a circuit is not formed, said secondsemiconductor chip being mounted on a circuit-formed front surface ofsaid first semiconductor chip through the second insulating adhesionlayer; each of said first and second semiconductor chips beingwire-bonded to the electrode section with a wire, said first and secondsemiconductor chips and the wire being sealed with a resin.
 2. Asemiconductor device including a stacked package structure and a chipsize package structure, comprising: an insulating substrate including awiring layer having electrode sections; a first semiconductor chiphaving a paste applied to its back surface where a circuit is notformed, said first semiconductor chip being mounted on said wiring layerthrough said paste; and a second semiconductor chip having a secondadhesion layer adhered to its back surface where a circuit is notformed, said second semiconductor chip being mounted on a circuit-formedfront surface of said first semiconductor chip through the secondadhesion layer; each of said first and second semiconductor chips beingwire-bonded to the electrode section with a wire, said first and secondsemiconductor chips and the wire being sealed with a resin.
 3. Asemiconductor device comprising: an insulating substrate including awiring layer having electrode sections; a first semiconductor chiphaving a circuit forming on its front surface and an adhesion layeradhered to its back surface; a metal bump, disposed between said firstsemiconductor chip and said wiring layer, for bump-bonding the frontsurface of said first semiconductor chip to said wiring layer so thatthe front surface faces said wiring layer; and a second semiconductorchip whose back surface where a circuit is not formed is mounted on theback surface of said first semiconductor chip through the adhesionlayer; said second semiconductor chip being wire-bonded to the electrodesection of said wiring layer with a wire, said first and secondsemiconductor chips and the wire being sealed with a resin.
 4. Thesemiconductor device as set forth in claim 3, wherein the back surfacesof said first and second semiconductor chips have a same shape.
 5. Thesemiconductor device as set forth in claim 3, further comprising a lightblocking layer, disposed between said first semiconductor chip and saidwiring layer, for blocking a light incident from said insulatingsubstrate.
 6. The semiconductor device as set forth in claim 1, wherein,when said first and second semiconductor chips have different shapes, asupport member is used for supporting and fixing a protruding part ofthe back surface of said second semiconductor chip, which is not facingsaid first semiconductor chip, said support member having a same shapeas the protruding part.
 7. The semiconductor device as set forth inclaim 2, wherein, when said first and second semiconductor chips havedifferent shapes, a support member is used for supporting and fixing aprotruding part of the back surface of said second semiconductor chip,which is not facing said first semiconductor chip, said support memberhaving a same shape as the protruding part.
 8. The semiconductor deviceas set forth in claim 3, wherein, when said first and secondsemiconductor chips have different shapes, a support member is used forsupporting and fixing a protruding part of the back surface of saidsecond semiconductor chip, which is not facing said first semiconductorchip, said support member having a same shape as the protruding part. 9.The semiconductor device as set forth in claim 6, wherein said supportmember has a same coefficient of linear expansion as said secondsemiconductor chip.
 10. The semiconductor device as set forth in claim7, wherein said support member has a same coefficient of linearexpansion as said second semiconductor chip.
 11. The semiconductordevice as set forth in claim 8, wherein said support member has a samecoefficient of linear expansion as said second semiconductor chip. 12.The semiconductor device as set forth in claim 1, wherein one end of thewire for connecting said first semiconductor chip to said wiring layerand the wire for connecting said second semiconductor chip to saidwiring layer are connected in a first electrode pad disposed on saidfirst semiconductor chip and a second electrode pad disposed on saidsecond semiconductor chip, respectively, and the other ends of the wiresare connected to the electrode sections of said wiring layer.
 13. Thesemiconductor device as set forth in claim 2, wherein one end of thewire for connecting said first semiconductor chip to said wiring layerand the wire for connecting said second semiconductor chip to saidwiring layer are connected to a first electrode pad disposed on saidfirst semiconductor chip and a second electrode pad disposed on saidsecond semiconductor chip, respectively, and the other ends of the wiresare connected to the electrode sections of said wiring layer.
 14. Thesemiconductor device as set forth in claim 12, wherein the wireconnected to the first electrode pad in one end is a first wire and thewire connected to the second electrode pad in one end is a second wireand when the other ends of the first and second wires are bonded to thesame electrode section, the electrode section is arranged to have afirst electrode portion to which the first electrode pad is connectedwith the first wire and a second electrode portion to which the secondelectrode pad is connected with the second wire.
 15. The semiconductordevice as set forth in claim 13, wherein the wire connected to the firstelectrode pad in one end is a first wire and the wire connected to thesecond electrode pad in one end is a second wire, and when the otherends of the first and second wires are bonded to the same electrodesection, the electrode section is arranged to have a first electrodeportion to which the first electrode pad is connected with the firstwire and a second electrode portion to which the second electrode pad isconnected with the second wire.
 16. The semiconductor device as setforth in claim 12, wherein the wire connected to the first electrode padin one end is a first wire and the wire connected to the secondelectrode pad in one end is a second wire, and when the first and secondelectrode pads are bonded to the same electrode section, the first andsecond electrode pads are connected to each other by connecting theother end of the second wire to the first electrode pad, and the firstelectrode pad is connected to the electrode section with the first wire.17. The semiconductor device as set forth in claim 13, wherein the wireconnected to the first electrode pad in one end is a first wire and thewire connected to the second electrode pad in one end is a second wire,and when the first and second electrode pads are bonded to the sameelectrode section, the first and second electrode pads are connected toeach other by connecting the other end of the second wire to the firstelectrode pad, and the first electrode pad is connected to the electrodesection with the first wire.
 18. The semiconductor device as set forthin claim 12, wherein the wire connected to the first electrode pad inone end is a first wire and the wire connected to the second electrodepad in one end is a second wire, and when the other ends of the firstand second wires are bonded to different electrode sections, a dummy padis provided on the first semiconductor chip so as to connect the secondelectrode pad to said wiring layer with the second wire via the dummypad.
 19. The semiconductor device as set forth in claim 13, wherein thewire connected to the first electrode pad in one end is a first wire andthe wire connected to the second electrode pad in one end is a secondwire, and when the other ends of the first and second wires are bondedto different electrode sections, a dummy pad is provided on the firstsemiconductor chip so as to connect the second electrode pad to saidwiring layer with the second wire via the dummy pad.
 20. Thesemiconductor device as set forth in claim 3, further comprising aninsulating layer for preventing degradation of said metal bump, saidinsulating layer being disposed between said first semiconductor chipand said wiring layer.
 21. The semiconductor device as set forth inclaim 20, wherein said insulating layer includes a layer having a lightblocking property and a size arranged so as not to come into contactwith said metal bump.
 22. The semiconductor device as set forth in claim3, further comprising a filling material for preventing degradation ofsaid metal bump, said filling material being filled between said firstsemiconductor chip and said wiring layer.
 23. A semiconductor devicecomprising: an insulating substrate including a wiring layer on itssurface and a packaging-use external terminal on its back surface, thewiring layer having an electrode section, the packaging-use externalterminal being electrically connected to said wiring layer through a viahole; a first semiconductor chip produced by forming a first adhesionlayer on a back surface of a wafer having a desired circuit formed onits front surface and by dicing the wafer, said first semiconductor chipbeing mounted on said insulating substrate through the first adhesionlayer; and a second semiconductor chip produced by forming a secondadhesion layer on a back surface of a wafer having a circuit formed onits front surface and by dicing the wafer, said second semiconductorchip being mounted on a circuit-formed surface of said firstsemiconductor chip through the second adhesion layer; said first andsecond semiconductor chips being connected to the electrode section ofthe wiring layer with a wire, said first and second semiconductor chipsand the wire being sealed with a resin.
 24. A semiconductor devicecomprising: an insulating substrate including a wiring layer on itsfront surface and a packaging-use external terminal on its back surface,the wiring layer having an electrode section, the packaging-use externalterminal being electrically connected to said wiring layer through a viahole; a first semiconductor chip having a desired circuit formed on itsfront surface, said first semiconductor chip being mounted through aninsulating paste; and a second semiconductor chip produced by forming aan second insulating adhesion layer on a back surface of a wafer havinga desired circuit formed on its front surface and by dicing the wafer,said second semiconductor chip being mounted on a circuit-formed surfaceof said first semiconductor chip through the second insulating adhesionlayer; said first and second semiconductor chips being connected to theelectrode section of the wiring layer with a wire, said first and secondsemiconductor chips and the wire being sealed with a resin.
 25. Thesemiconductor device as set forth in claim 23, wherein, when an outeredge of said second semiconductor chip protrudes from an outer edge ofsaid first semiconductor chip, a support member having a same thicknessas said first semiconductor chip is provided under a protruding part ofsaid second semiconductor chip.
 26. The semiconductor device as setforth in claim 24, wherein, when an outer edge of said secondsemiconductor chip protrudes from an outer edge of said firstsemiconductor chip, a support member having a same thickness as saidfirst semiconductor chip is provided under said second semiconductorchip.
 27. A semiconductor device comprising: a first semiconductor chip;an insulating substrate including on its front surface a wiring layerhaving an electrode section; an insulating layer disposed in an areawhere said first semiconductor chip is to be mounted, except for a partto be connected to said first semiconductor chip; and a metal bump formaking electrical connection to said first semiconductor chip, saidinsulating substrate including on its back surface a packaging-useexternal terminal electrically connected to said wiring layer through avia hole, said first semiconductor chip being mounted on the frontsurface of said insulating substrate by face-down bonding through saidmetal bump; and a second semiconductor chip produced by forming a firstadhesion layer on a back surface of a wafer having a desired circuitformed on its front surface and by dicing the wafer, said secondsemiconductor chip being mounted on a surface of said firstsemiconductor chip on which surface a circuit is not formed, through thefirst adhesion layer; said second semiconductor chip being connected tothe electrode section of the wiring layer with a wire, said first andsecond semiconductor chips and the wire being sealed with a resin. 28.The semiconductor device as set forth in claim 27, wherein theinsulating layer includes a light blocking layer.
 29. The semiconductordevice as set forth in claim 27, wherein, when an outer edge of saidsecond semiconductor chip protrudes from an outer edge of said firstsemiconductor chip, a support member having a same thickness as saidfirst semiconductor chip is provided under a protruding part of saidsecond semiconductor chip.
 30. A method of manufacturing a semiconductordevice comprising the steps of: (a) forming a first insulating adhesionlayer on a back surface of a first wafer having a circuit formed on itsfront surface; (b) producing separate first semiconductor chips fromsaid first wafer by dicing; (c) mounting said first semiconductor chipon a wiring layer with its back surface facing said wiring layer; (d)forming a second insulating adhesion layer on a back surface of a secondwafer having a circuit formed on its front surface; (e) producingseparate second semiconductor chips from said second wafer by dicing;(f) mounting said second semiconductor chip on said first semiconductorchip with its back surface facing said first semiconductor chip; (g)wire-bonding said first semiconductor chip to an electrode section ofsaid wiring layer with a wire; (h) wire-bonding said secondsemiconductor chip to an electrode section of said wiring layer with awire; and (i) sealing said first and second semiconductor chips and thewires.
 31. A method of manufacturing a semiconductor device comprisingthe steps of: (a) forming an insulating layer and a metal bump on awiring layer; (b) mounting a first semiconductor chip on said wiringlayer with its circuit-formed surface facing said wiring layer; (c)forming an insulating adhesion layer on a back surface of a wafer havinga circuit formed on its front surface; (d) producing separate secondsemiconductor chips from the wafer by dicing; (e) mounting said secondsemiconductor chip on said first semiconductor chip with it back surfacefacing said first semiconductor chip; (f) wire-bonding said secondsemiconductor chip to said wiring layer with a wire; and (g) sealingsaid first and second semiconductor chips and the wire.
 32. The methodof manufacturing the semiconductor device as set forth in claim 30,further comprising the steps of: (j) forming a metal ball on each end ofthe wire for connecting said second semiconductor chip to the electrodesection of the wiring layer; (k) connecting one of the metal balls tosaid second semiconductor chip; (l) cutting said wire; and (m) making asurface of the metal ball connected to said second semiconductor chipflat; said steps (j) to (m) being included between said steps (g) and(h).
 33. The method of manufacturing the semiconductor device as setforth in claim 31, further comprising the steps of: (h) forming a metalball on each end of the wire; (i) connecting one of the metal balls tosaid second semiconductor chip; (j) cutting the wire; and (k) making asurface of the metal ball connected to said second semiconductor chipflat; said steps (h) to (k) being included between said steps (e) and(f).